It has long been recognized that electrical current will induce a magnetic field, and that a moving magnetic field can induce current, or changes in the magnitude of a pre-existing current. One conventional application of this phenomenon is the transducer for converting between current and vibration. More particularly, a transducer for converting between vibration and current can: (1) convert linear mechanical vibration (e.g., acoustic vibration) into a pattern of variations in electrical current; and/or (2) convert variations in a current into vibration. Such a transducer can be used to produce electrical signals from the vibrations of a musical instrument, such as a guitar.
In a guitar, taut strings are vibrated to induce acoustic vibrations in the guitar body and the air surrounding the guitar. One or more transducers may be fixed to some part of the guitar. The vibrations of the guitar induce relative vibration between a coil and a permanent magnet in each transducer. This induced relative vibration causes current patterns in the coil. The current in the coil is usually amplified and sent to a speaker to produce louder and better-directed sound corresponding to the vibration of the guitar.
A variety of transducers have been used to convert the vibrations of a guitar into electrical current patterns. One common type involves the use of one or more piezoelectric crystals. However, such transducers suffer from a number of known drawbacks. One drawback is that piezocrystals tend to produce an unattractive sound distortion that is especially problematic when amplified.
Some guitars, such as disclosed in U.S. Pat. No. 5,898,121, employ string sensors or pickups, which are disposed generally beneath the strings and are adapted to convert the vibrational energy from the strings into electrical signals that can be amplified. Other guitars, such as disclosed in U.S. Pat. No. 3,624,264, use sensors attached to the guitar soundboard to translate the motion of the soundboard into electrical signals. One drawback of using conventional transducers as string sensors is that they only vibrate linearly, thereby limiting sound quality characteristics in the areas of feedback, attach, sustain, equalization and dynamic range.
In view of the above, there exists a need for a transducer having improved vibrational characteristics for producing high quality sound.